1. Field of the Invention
This invention provides a method of continuously coating a particulate material with a resin in the presence of an aqueous gel. The product of the method, a resin-coated particulate material, is especially useful in the treatment of subterranean oil and gas producing formations for the purpose of forming consolidations of the particulate material therein. The consolidations function to help control loose formation sand and to help retain loose proppants placed in fractures formed therein.
2. Description of the Prior Art
Processes and techniques have been developed for consolidating particulate material, e.g., sand, into a hard permeable mass in a subterranean zone.
These processes are useful in treating a subterranean formation containing loose or incompetent sands which migrate with hydrocarbons produced therefrom. The consolidated particulate material reduces or prevents such migration when it is placed between the producing formation and the well bore penetrating the formation. The formation of the consolidated, permeable, particulate mass has been accomplished by coating formation sand adjacent the well bore with a hardenable resin, and then causing the resin to harden. An alternate technique has been to coat sand with a resin on the surface, to suspend the coated sand in a carrier liquid and then to pump the suspension by way of the well bore into the formation containing loose or incompetent sands to deposit the coated sand therein. The resin on the deposited sand is then caused or permitted to harden whereby a consolidated, hard permeable mass is formed between the well bore and the loose or incompetent sands in the formation.
The previously developed methods have been used successfully in applications featuring resin coating of particulate material by batch mixing of component streams, but these methods have not been desirable in applications which require the rapid coating of particulate material suspended in continuous streams of a carrier liquid. For example, it is often necessary that resin-coated particulate material be continuously carried into a subterranean formation by a gelled aqueous carrier liquid for a relatively long period of time in order to deposit the resin-coated material and hold it in place against the face of the formation or to deposit the material in fractures formed in the formation. In such applications, if the flow rate of the carrier liquid is reduced or interrupted, the resin coated particulate material carried in the liquid can be deposited in undesired locations such as in surface equipment or in the well bore instead of in formation fractures or other specific desired locations.
The batch mixing methods for producing continuous streams of gelled aqueous carrier liquids containing resin coated particulate materials are time-consuming and expensive and are attended by risks of flow rate interruption or reduction. For example, U.S. Pat. No. 4,074,760 describes a method of forming a consolidated particulate mass in a subterranean formation wherein sand, coated with a resin, is suspended in a gelled aqueous carrier liquid. The carrier liquid is introduced into a subterranean zone whereby the resin coated sand is deposited and subsequently consolidated therein. The preparation of the suspension of carrier liquid and coated sand involves the batch mixing of components, i.e., the gelled aqueous carrier liquid containing sand is prepared separately from the resin followed by the batch mixing of the two for the period of time required to coat the sand with the resin.
U.S. Pat. No. 4,199,484 discloses a method of preparing a suspension of a particulate material coated with an epoxy resin in a gelled aqueous carrier liquid wherein the coating of the sand is carried out in the gelled aqueous carrier liquid. According to this method, the gelled carrier liquid, sand and other components are first combined followed by the addition of the epoxy resin with mixing whereby the epoxy resin coats the sand. The batch mixing of the components requires a period of time, e.g., at least about 15 minutes to several hours to obtain satisfactory coating of the particulate material before the slurry may be introduced into a placement zone. These prior art methods for forming suspensions of gelled aqueous carrier liquid and resin coated particulate material are not carried out on a substantially instantaneous and continuous basis.